Optically anisotropic bodies included in liquid crystal displays, such as a phase-retardation film or a polarizing plate, are produced by applying a solution containing a polymerizable liquid crystal compound to a rubbed base material or a base material including a photo-aligned film disposed thereon, drying the resulting coating film in order to remove the solvent, and causing polymerization using ultraviolet radiation or heat. In order to increase the viewing angles of liquid crystal displays, phase-retardation films are required to have an optical property such that the wavelength dispersion of birefringence (Δn) is small or reversed. Accordingly, polymerizable compounds having a reversed-dispersion property have been developed in order to achieve such a property (e.g., PTL 1). Note that, when the slope of a graph prepared by plotting the wavelength λ of light incident to a phase-retardation film in the horizontal axis and the corresponding birefringence (Δn=refractive index ne measured using extraordinary light−refractive index n0 measured using ordinary light) in the vertical axis is positive (rising to the right), it is commonly said that “the birefringence of the phase-retardation film has reversed-wavelength dispersion” or “the polymerizable compound constituting the phase-retardation film has a reversed-dispersion property”.
One of the methods for converting a polymerizable compound constituting a phase-retardation film to be a polymerizable compound having a reversed-dispersion property is to introduce a portion (vertical unit) that has a large birefringence in a direction perpendicular to the longer axis of the molecule into the molecule. However, introducing the vertical unit into the molecule is likely to degrade the liquid crystal property and alignment property of the polymerizable compound. This requires a certain times of tests to be conducted in order to produce a polymerizable compound that does not degrade the alignment property.
When a polymerizable compound is applied to a base material, an adequate amount of polymerizable compound needs to be dissolved in a solvent that does not corrode the base material. However, the introduction of the vertical unit is likely to degrade the solubility of the polymerizable compound in the solvent. This results in failure to prepare a solution having a sufficiently high concentration. In addition, crystals may precipitate while the solution is stored.
The introduction of the vertical unit also changes the absorption spectrum of the polymerizable compound. Specifically, the absorption band shifts to longer-wavelength region in many cases. This is likely to degrade the optical stability of the compound and leads to, for example, yellowing of a phase-retardation film and cracking in a phase-retardation film.